w
w
ap
eP
m
e
tr
.X
w
UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS
s
er
om
.c
GCE Ordinary Level
MARK SCHEME for the October/November 2007 question paper
5070 CHEMISTRY
5070/03
Paper 3 (Practical Test), maximum raw mark 40
This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of
the examination. It shows the basis on which Examiners were instructed to award marks. It does not
indicate the details of the discussions that took place at an Examiners’ meeting before marking began.
All Examiners are instructed that alternative correct answers and unexpected approaches in
candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills
demonstrated.
Mark schemes must be read in conjunction with the question papers and the report on the
examination.
•
CIE will not enter into discussions or correspondence in connection with these mark schemes.
CIE is publishing the mark schemes for the October/November 2007 question papers for most IGCSE,
GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level
syllabuses.
Page 2
1
Mark Scheme
GCE O LEVEL – October/November 2007
Syllabus
5070
Paper
03
(a) Titration
Accuracy
10 marks
For the two best titres give:
5 marks for a value within 0.2 cm3 of supervisor
3 marks for a value within 0.3 cm3 of supervisor
2 marks for a value within 0.4 cm3 of supervisor
1 mark for a value within 0.5 cm3 of supervisor
Concordance 3 marks
Give:
3 marks if all the ticked values are within 0.2 cm3
2 marks if all the ticked values are within 0.3 cm3
1 mark if all the ticked values are within 0.4 cm3
Average
1 mark
Give 1 mark if the candidate calculates a correct average (error not greater than 0.05) of all
his ticked values.
[14]
© UCLES 2007
Page 3
Mark Scheme
GCE O LEVEL – October/November 2007
Syllabus
5070
Paper
03
(b) Assuming a 25 cm3 pipette and a titre of 24.6 cm3
Concentration of hydrochloric acid, in mol/dm3
conc =25.0 x 0.1 (1)
24.6
= 0.102 (correct to 0.001) (1)
[2]
(c)(d) R + P
Effervesces (bubbles etc) (1)
Turns limewater milky etc. (1)
Carbon dioxide evolved (1)
Colourless or clear solution remains or partially soluble or some dissolves (1)
ZnCO3 circled or indicated (1)
Carbon dioxide named or tested for (with limewater) or effervesces etc.
© UCLES 2007
[5]
Page 4
Mark Scheme
GCE O LEVEL – October/November 2007
Syllabus
5070
Paper
03
Question 2
S is Cu(NH3)4SO4
Test
General points
For ppt
allow solid, suspension, powder
[23]
Notes
For gases
Name of gas requires test to be at least partially correct.
Effervesces = bubbles = gas vigorously evolved (but not just gas evolved)
Solutions
Colourless not equivalent to clear, clear not equivalent to colourless
Test 1
4 marks
Blue ppt (1)
Allow shades of blue here and elsewhere. Allow
blue/green here but not elsewhere (for ppts)
Turns black (1)
Allow brown, no need to link to solid, allow brown ‘stain’
etc.
Gas turns litmus blue (1)
Allow turns litmus blue (without gas) if ammonia
mentioned, fumes with HCl
Ammonia (1)
Test 2
4 marks
Blue ppt (2)
Give one mark for ppt of whatever colour.
Mixed coloured (white ppt + blue ppt) do not score the
colour mark here or in Test 3
Soluble in acid (1)
Blue solution (1)
Allow green but not colourless
Allow paler blue solution even if ppt remains
Test 3
4 marks
White ppt (2)
Give one mark for ppt of whatever colour.
Insoluble in acid (1)
Solution becomes colourless (1)
or paler
Allow pale blue but not blue unless solution earlier is
dark blue
© UCLES 2007
Page 5
Mark Scheme
GCE O LEVEL – October/November 2007
Syllabus
5070
Paper
03
Test 4
9 marks
No initial reaction with KI (1)
Allow slight colour change but not (turns) blue
Any implication of a reaction effervesces loses this mark
+ acid
White ppt (2)
Yellow or brown solution (1)
Give one mark for a ppt of any colour. Give the colour of
ppt mark for anything than is paler/yellower than brown.
Ignore the order in which the colours appear and mixed
colours. Not orange for colour of ppt
Both colour and solution required if ppt mentioned but
turns yellow/brown (1) if nothing else in part (b), allow
orange for solution
+ thiosulphate
White ppt (1)
Allow pale pink, pale lilac for white
Solution is now colourless (1)
Ppt dissolves(1)
Forms a colourless solution (2)
Colourless solution (1)
White ppt reforms (1)
Allow any pale colour ppt or even turns cloudy/milky or
white solution at this stage i.e. after the earlier white ppt
has dissolved
Conclusion
2 marks
Allow any two of
Cu 2+ or copper(II) (1)
SO4 2– or sulphate (1)
Ppt of any colour in Test 3
NH4 +or ammonium (1)
Ammonia named or tested for in Test 1
© UCLES 2007